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Sen7cn - 2.05.6 <br />righu, monetary compensation, development of alternative watering facilities such as guzzlers, or <br />other appropriate mitigation measures. A copy of the Dirisicvr cf Water Raar~ Dmml Plan cf <br />Aegrrritatirv: is included in Exhibi[ 2.04-E4, Hydrologic Information. <br />Potential Acid- or Toxic-Producing Materials and Drainage -Comprehensive discussions of the <br />chemical characteristics of coal and other materials to be disturbed or handled in conjunction with <br />mining and related activities are presented in Section 2.04.6, Geology Description. Evaluation of all <br />available chemical analyses has resulted in no indications that the sampled materials are or will be <br />potentially acid- or toxic-fomwrg. In addition, both normal mine dewatering flows and discharge <br />from the flooded area of the potential mine fire have been monitored and there u no evidence of any <br />significant potential for development of acidic or toxic drainage az a result of any mine water <br />discharge or resaturation following mine abandonment and sealing. <br />While underground Honing and related operations and surface placement of mine development waste <br />tnatenals may result in minor shifts in surface and ground water chemistry and limited increases in <br />TDS levek and concentrations of specific chemical componenu, these changes in water quality will <br />be localized and are not expected to result in any significant adverse impacts on surface or ground <br />water systems or the planned postmining land use. Given these considerations, no special meazures <br />are necessary to control or mitigate potential impacts from acid- or toxic-forming materials although <br />mine drainage control, controlled placement and compaction of coal refuse and mine waste materiak, <br />off-site disposal of noncoal wastes, and sealing of mine openings will cenainly serve to .,,~~~rt,~~e any <br />potential minor impacrs. <br />Potential for Intemrption, Diminution, or Contamination of Water Supply Sources - As <br />previously discussed, OMI's mining and related operations are not expected to adversely impact any <br />surface or ground water sources or water righu. Consequently, these is no need to explicitly address <br />• provisions for replacement of impacted water rights at this time. In the unlikely event however, that <br />proxunate contamination, diminution, or interruption does occtu and can be documented az resulting <br />from their existing or proposed mining and related operations, OMI will mitigate the associated water <br />rights impacts through discussion and development of a cooperauve agreement with any effected <br />water rights holder(s). Potential mitigation options may include but will not be limited to replacement <br />or augmentation of effected water rights, monetary compensation, or development of alternative <br />watering facilities such az guzzles. OMI controls several senior water rights in the area which should <br />be more than sufficient to mitigate any impacts on beneficial water use resulting from potential <br />Honing-related impacts to the hydrologic balance. <br />The primarypostmining land use in the mine permit and adjacent areaz will be undeveloped land used <br />primarily for wildlife habitat, limited livestock grazing, and dispersed recreation. The proposed use <br />involves minimal supporting water requirements. The discussions presented in Section 2.04.7, <br />Hydrologic Description, indicate that while surface and ground water resources are limited in those <br />areas to be affected by the OMI operations, they will be adequate in terrtss of both quantity and <br />quality to support the designated postntinurg land use. Given the proposed postmining use, OMI <br />currently has no plans to transfer any exploration boreholes or monitoring wells for subsequent use <br />az water wells. <br />Potential Effects on Sediment Yields, Flooding, Stream Flows, and Surface or Grotmd Water <br />Availability -All temporary and pemtanent diversions wither the OMI permit area have been <br />designed and either have been or will be constructed to maintain effective flow under all anticipated <br />conditions. While underground rttinirtg operations may result in some ground subsidence, surface <br />subsidence will be limited to the areas shown on the Mme Plan Map, (Maps 2.05-M2). Subsidence is <br />estimated to be approximately 0.6 times the coal seam thickness and the area of subsidence will be <br />• minimal. Anticipated subsidence will result in some lowering of the ground surface over mined-out <br />areas and may result in development of surficial tensron cracks. T1te nature of surficial materials <br />should however, result in healing of any cracks within a short time period az coruolidation and <br />siltation result in collapse and filling of surface fractures. Subsidence, therefore, should not result in <br />PR04 2.05-97 Revised August 2000 <br />